When you send an e-mail, it is typically subjected to spam filtering. In some cases, your message may be incorrectly flagged as spam. This section explains why this can happen and how to prevent your e-mails from being marked as spam.
Main Causes
These are the three primary reasons an email may be flagged as spam:
- Your e-mail contains spam-sensitive words.
- The e-mail address you created contains spam-sensitive characters.
- The SPF record for your domain is not configured correctly.
Spam-sensitive words
A spam filter scans the content and subject of an e-mail for words commonly associated with spam (e.g., 'win' or 'free'). You should also avoid excessive use of capital letters, exclamation marks, and unnecessary spaces. Images and attachments with long or unclear filenames are also not recommended.
Some spam filters are configured very strictly. If your e-mail ends up in the recipient's spam folder, it is a good idea to review your message for spam-sensitive words and characters. If you find such terms, remove them and resend the e-mail.
Spam-sensitive e-mail address
It may happen that an e-mail address itself is considered spam-sensitive. Often, a combination of numbers and letters makes an address appear untrustworthy. For example, Xx_sp4m_s3ns1t1v3_xX@example.com. Make sure your e-mail address does not contain too many 'unusual' characters.
Incorrect SPF record
Some e-mail providers check the SPF record very strictly. The purpose of an SPF record is to verify that you are authorised to send email from a particular server. This SPF record should include both the IPv4 and IPv6 addresses.
Testing your e-mail address
Note that an e-mail with 'test' in the subject and little to no content is usually flagged as spam and blocked immediately. If you want to test your e-mail, always send a message that appears legitimate.